Fibre Channel Input/Output Data Routing System and Method

1. A method of performing an input/output (I/O) processing operation at a host computer system configured for communication with a control unit, the method comprising: obtaining, by the channel processor, information relating to an I/O operation at a channel subsystem in the host computer system, the channel subsystem including at least one channel having a channel processor and a local channel memory, the channel processor configured to execute instructions stored in a computer readable storage medium; generating, by the channel processor, an address control structure for each of a plurality of consecutive data transfer requests specified by the I/O operation and forwarding each address control structure from the at least one channel to a network interface between the channel subsystem and at least one I/O device, each address control structure specifying a location in the local channel memory of a corresponding address control word (ACW), each address control structure including an Offset field indicating a relative order of a corresponding data transfer request relative to other data transfers in the plurality of consecutive data transfer requests; generating, by the channel processor, at least one ACW specifying one or more host memory locations for the plurality of consecutive data transfer requests, and storing the at least one ACW in the local channel memory, the at least one ACW including an Expected Offset field indicating a relative order of an expected data transfer request; forwarding an I/O command message to the at least one I/O device via the network interface; in response to the I/O command message, receiving a data transfer request from the network interface that includes the addressing information specified by a corresponding address control structure; comparing, by a data router in the channel, the Offset field and the Expected Offset field to determine whether the data transfer request has been received in the correct order; and based on determining that the data transfer request has been received in the correct order, accessing the at least one ACW by the data router and routing the data transfer request to the host memory location specified in the at least one ACW.

2. The method of claim 1 , wherein routing the data transfer request includes incrementing the Expected Offset field value by an amount corresponding a size of the data transfer request.

3. The method of claim 1 , wherein receiving the data transfer request includes routing the data transfer request to request queue that includes at least one of a Fetch Array Queue configured to hold two or more consecutive output data requests for output data in the host memory, and a Store Array Queue configured to hold two or more consecutive input data requests to store input data at the host memory.

4. The method of claim 3 , wherein receiving the data transfer request includes receiving each of the plurality of consecutive data transfer requests and storing each of the plurality of data transfer requests in the request queue in the order received and processing each of the plurality of data transfer requests from the request queue in the order received.

5. The method of claim 4 , further comprising, based on the Expected Offset field not matching the Offset field of the data transfer request, re-queuing the data transfer request at an end of the request queue.

6. The method of claim 5 , further comprising: processing one or more of the plurality of data transfer requests in order from the request queue until the data transfer request reaches the top of the request queue; comparing the Expected Offset field to the Offset field of the data transfer request; and based on the Expected Offset field matching the Offset field, accessing the at least one ACW by the data router and routing the data transfer request to the host memory location specified in the at least one ACW; based on the Expected Offset field not matching the Offset field, discarding the corresponding data transfer requests and any other subsequent data transfer requests in the plurality of requests.

7. The method of claim 5 , further comprising: setting a time stamp and writing the time stamp into the data transfer request prior to re-queuing the data transfer request, wherein upon the data transfer request reaching the top of the request queue and the Expected Offset field not matching the Offset field, performing one of: based on the time stamp exceeding a selected timeout value, discarding the data transfer request and any other subsequent data transfer requests in the plurality of requests; and based on the time stamp not exceeding a selected timeout value, re-queuing the data transfer request at the end of the request queue.

8. The method of claim 1 , wherein the I/O operation is a transport mode operation, and obtaining information includes obtaining a transport command word (TCW) at the channel subsystem, the TCW including a transport command control block (TCCB) address field including an address of a TCCB, the TCCB including a plurality of device command words (DCW) that each includes an I/O command.